1. Field of the Invention
The present invention relates to liquid shut-off valves and in particular, shut-off valves for use with a tankless water heater.
2. Background Art
Tankless water heaters are a class of water heaters which have minimal reservoir volume and heat hot water on demand when needed. Tankless water heaters are frequently located near the point of use in order to minimize the volume of water between the water heater and the point of use which typically goes to waste after hot water use is terminated. Further energy savings occurs due to the fact that the water is only heated on demand therefore there is no large hot water reservoir constantly leaking heat to the environment even during long periods of inactivity.
Due to the small liquid volume within a tankless hot water heater, it is frequently necessary to periodically drain and flush the tankless water heater to prevent or eliminate scale build up.
FIG. 1 illustrates a common plumbing installation for tankless water heater 20 which has a cold water inlet 22 and a hot water outlet 24. Tankless hot water heater 20 will be provided typically with an internal electric heating element (not shown), heating an internal conduit extending between inlet 22 and outlet 24. Cold water comes into the system via cold water inlet pipe 26 passing through a first shut off valve 28 which is typically a ¼ turn ball valve having an open and close position. Valve 28 of course can have other valve constructions such as that of a gate valve or the like. Interposed between valve 28 and cold water inlet 22 is a T-branch connection 30 coupled to an auxiliary inlet/outlet valve 32. Valve 32 is provided with an inlet/outlet 34 which is normally closed by cap 36. In normal use, valve 28 is open and valve 32 is closed.
The hot water outlet 24 of tankless water heater 20 is connected to a hot water outlet pipe 38 by a fluid line having a shut off valve 40 which is preferably, a ¼ turn ball valve, but alternatively, can be a gate valve or the like. Between shut off valve 40 and the hot water outlet, a T-branch connection 42 is provided for mounting an auxiliary shut off valve 44 having an inlet/outlet 46 removably closed by cap 48. Ideally, a pressure relief valve 50 is provided in the system to let hot water escape in the event an extremely high pressure condition occurs. In normal operation, water flows through tankless water heater 20 in the direction of the in and out arrows illustrated in FIG. 1. When one desires to flush the system, valves 28 and 40 are closed and, valves 32 and 44 are opened. Caps 36 and 48 are removed from outlets 34 and 46 so the system may be drained and water or other flushing fluid run through the heater to remove scale build up. While the system of valves illustrated in FIG. 1 functions satisfactorily, the valves are relatively expensive and occupy a fair amount of space.
An object of the present of invention is to make a low cost valve assembly for use with a tankless water heater. It is further an object of the present invention to provide a very compact valve system so that the tankless water heater can be mounted in a tight space.